1. Field of the Invention
The present invention relates to a dish washing machine and a dish washing and drying machine for automatically, for example, washing, rinsing, and dehydrating the drying dishes contained in a cavity.
2. Description of the Prior Art
A dish washing and drying machine so adapted as to spray wash water on the dishes contained in a cavity to wash the dishes and dry the dishes which have been washed in the cavity is known and is disclosed in, for example, Japanese Patent Laid-Open Gazette No. 48724/1985.
A conventional dish washing and drying machine is so constructed that at least a part of the sidewall of a water suction pipe provided between a water storage chamber provided on the bottom of a cavity and the water suction side of a nozzle pump is made of a translucent material, and a light emitting element and a light receiving element for detecting the light transmittance of a liquid in the water suction pipe are disposed on the outside of the translucent sidewall, to control the termination of each of the washing, rinsing, dehydrating and drying processes at the time point where the amount of light received by the light receiving element is not changed.
Meanwhile, dirt on the dishes to be washed by the dish washing and drying machine is not uniform. Accordingly, it is desirable to change how to wash the dishes depending on the type of dirt.
Although it is generally desirable that oily dirt is removed by increasing the temperature of wash water to soften the oil, dirt by proteins such as albumin in eggs must be removed with low-temperature wash water because it solidifies at high temperatures (not less than 60.degree. C.).
In the conventional dish washing and drying machine, however, washing process control corresponding to the quality of dirt, such as oily dirt or dirt by proteins is not carried out. In the conventional dish washing and drying machine, therefore, an oil film may remain or a residue of eggs or the like may remain stuck on the dishes which have been washed.
Furthermore, the conventional dish washing and drying machine has the disadvantage in that light transmittance proportional to the condition of dirt of wash water itself cannot, in some cases, be detected. The following are the reasons. A detergent dissolves in the wash water in the washing process. Accordingly, bubbles of the detergent are formed if the wash water is agitated at the time of washing. In addition, if air is mixed with the wash water during the circulation of the wash water, cavitation is encountered, to form fine bubbles. The bubbles change the light transmittance of the wash water. Therefore, the light transmittance of the wash water itself may not, in some cases, be accurately detected.
Furthermore, garbage debris dropped from the dishes is suspended in the wash water during the washing operation. Accordingly, the garbage may, in some cases, cross between the light emitting element and the light receiving element, thereby preventing light transmittance of the wash water from being detected.